Size effects on the electrochemical oxidation of oxalic acid on nanocrystalline platinum

The electrocatalytic activity of platinised platinum (Pt \ Pt) electrodes i n the electrooxidation of oxalic acid was found to be dependent on the degr ee of ageing. Pt \ Pt electrodes prepared by electrodeposition were aged by cycling the potential with an upper positive potential limit corresponding to Pt surface oxidation. This procedure results in surface reconstruction with an increase of mean particle size. The changes of surface area and rou ghness of Pt \ Pt during ageing have been discussed in terms of sintering p rocesses for supported catalysts or ceramic materials. An increase of mean particle size is accompanied by a decrease in oxygen adsorption, e.g. throu gh changes in the surface concentration of defects on the particle surface. Two possible mechanisms for the electrooxidation of oxalic acid involving either an oxygen adsorbate species (CE mechanism) or direct electrode trans fer can be distinguished. Changes of oxidation rate are related to changes of oxygen coverage with ageing. (C) 2000 Elsevier Science S.A. All rights r eserved.